The present invention relates to a marine propulsion and ship's drive system, having a drive train, including a gear transmission for connecting an engine to a propeller shaft, and further having a branch and auxiliary shaft drivingly connected to that drive train for powering auxiliary equipment.
Marine propulsion and ship drive systems of the type to which the invention pertains include usually an engine with an output shaft; a propeller shaft; and a speed-reducing, clutch-controlled transmission gear system connecting the engine shaft to the propeller shaft. The branch and auxiliary shaft means are connected to that transmission for deriving power from the main engine, e.g., for driving electric generators, hydropumps, compressors, and/or other auxiliary systems and devices.
Depending upon the particulars of a branch, it may be designed as primary branch or secondary branch; the first variety can be driven independently from the propeller, the second variety operates only when the propeller is driven. Moreover, a secondary branch is dependent upon the operating state of the engine. Many modern ships have propellers with adjustable pitch so that the engine can run with a constant speed; different operating conditions and a variety of cruising speeds and conditions of the vessel are accommodated by propeller adjustment. Particularly in the case of a Diesel engine, this type of operation permits optimization of the engine. In general, such optimization, however, requires a lower, constant speed for particular low power operations, such as low speed maneuvering, or the like. Hence, at least two engine speeds are needed in order to cover the entire range of operational speeds of the vessel. On the other hand, some auxiliary equipment, such as generators, require constant input speed throughout (including the case when the ship's propeller has been stopped entirely). Thus, in the case of a secondary power branch system, one needs additional adjustable transmission means to ensure a constant generator speed, independently from the engine speed variations.